The present invention relates to a product manufacturing method, particularly for tobacco items.
In the following description, specific reference is made, purely by way of example, to a method of producing and processing cigarettes.
In general, cigarettes are produced and processed on a production line comprising a number of individual machines arranged in series, and each of which provides for a specific processing function, and is so operated as to accommodate the cigarette supply from the adjacent upstream machine.
In its most general form, such a line comprises a machine for producing cigarette portions; a filter assembly machine for producing filter-tipped cigarettes; a packing machine for forming groups of filter-tipped cigarettes into packets; a cellophaning machine for overwrapping each packet with a sheet of transparent material; a cartoning machine for grouping and forming the packets into cartons; a wrapping machine for overwrapping each carton; a boxing machine for grouping and loading the cartons into boxes; and a pallet loading machine for grouping and loading the boxed cartons on to a pallet.
Clearly, therefore, such a line comprises a number of handling machines, such as the filter assembly, cellophaning and wrapping machines, each of which provides for a specific handling operation of the incoming products from the adjacent upstream machine; and a number of grouping machines, each of which provides for forming the incoming products from the adjacent upstream machine into groups of a given number of products.
On such a line, each handling machine is normally operated "in time" with the adjacent upstream machine, i.e. the machine preceding it in the traveling direction of the cigarettes, and is connected to the upstream machine by a "rigid" type transfer device, at times with a compensating store.
Each grouping machine, on the other hand, is connected to the adjacent upstream machine by a respective transfer device which normally provides, between the machines, for a "flexible" type connection featuring either a product reintegrating or compensating store. In this case, the two machines do not operate in time with each other, and the products are fed in disorderly manner between the upstream and downstream machines, and are received in orderly manner by the downstream machine. In other words, with a flexible connection of the type still widely used for feeding products to a grouping machine, the products are fed in orderly manner off the upstream machine, and are subsequently disordered, only to be re-ordered for supply to the downstream machine.
The above operating mode is described, for example, in Patent DE-OS 31 20 674, in which the cigarettes coming off the manufacturing machine are fed in bulk to a feedbox with a number of output channels, each designed to feed a respective seat on an ordering drum by which the cigarettes are formed into a complete orderly sequence for supply to a follow-up packing machine.
A similar operating mode obviously involves a considerable waste of energy as well as a number of drawbacks mainly due to the sequence of handling operations to which the products are subjected.
One proposal for overcoming the above drawbacks has been to connect the grouping machine to the adjacent upstream machine by means of a rigid connection featuring a reintegrating device. In this case, the two machines are permanently synchronized with each other, and the products coming off the upstream machine are transferred synchronously to the downstream machine in the same orderly configuration in which they were fed off the upstream machine. As both machines are connected synchronously, the reintegrating device provides for supplying products with which to fill one or more gaps or one or more vacancies occurring at the output of the upstream machine. Here and hereinafter, the terms "vacancy" and "gap" are intended to mean the space formed on the connecting line between the two machines by the absence of one or a number of consecutive products respectively, which gaps and/or vacancies would, in the absence of reintegration, result in a shortage of one or more units in the product group formed on the downstream machine, and consequently in rejection of the incomplete group.
The above operating mode is described, for example, in Patents DE-PS 33 19 390 and DE-OS 37 05 941, in which the cigarettes coming off the manufacturing machine are fed to the packing machine by means of an intermediate feed device which receives a discontinuous sequence of cigarettes, and feeds them along an internal path which gets one step shorter for each vacancy in the discontinuous sequence, so as to convert the discontinuous sequence into a continuous one for supply to the packing machine. When the number of compensated vacancies equals the number of cigarettes in the packet formed on the packing machine, the original length of the internal path is restored, so as to feed to the packing machine a sequence containing a gap consisting of a succession of vacancies equal to the number of cigarettes in each packet. Upon the gap arriving at the input of the packing machine, this provides for performing a no-load cycle.
A similar operating mode presents numerous drawbacks, mainly due to the fact that the location of the gap in the sequence supplied to the packing machine, or more generally the downstream grouping machine, depends on the manner--purely random in general--in which the vacancies are presented.
One consequence of the above is that the grouping machine must be capable of performing a no-load cycle as of any point within the normal machine cycle. Apart from the fact that such a grouping machine in general, and a packing machine in particular, is still unheard of, even if it were to exist, it would fail to provide for entirely eliminating rejects, and would almost invariably result in the rejection of two incomplete groups upon arrival of each said gap. In fact, on almost all known grouping machines, the groups are formed, not continuously, but by first forming subgroups, and only in the event the start of said gap coincides with the start of one of the subgroups would it, perhaps, be possible to avoid said two rejects.